Drug use is normative in urban club scenes, with MDMA (ecstasy) and cocaine being the most prevalent club drugs. The parent grant which this application proposes to continue has documented not only high rates of mental health problems and extensive arrest and abuse histories, but also unexpectedly and alarmingly high rates of undiagnosed HIV infection among a predominately heterosexual young adult sample. The parent grant, now in its fifth year, is an 18-month longitudinal natural history study of 600 club and prescription drug using young adults. A key finding from that study is the extent to which the comprehensive health and social risk assessments induced participants to reduce their substance use and sexual risk behaviors. Over 70% of participants substantially reduced their substance use at the first follow-up assessment after baseline. Qualitative research with study completers showed that participants attributed the strong intervention effect of the baseline assessment to: 1) the friendly, non-judgmental field staff of age-peers; 2) the thorough and detailed assessments; and 3) an emerging self-awareness of substance use-related problems based on their responses to the assessment items. Study completers also reported that risk reduction tended to occur precisely because the study was not framed as an intervention. Within this context, the specific aims of the proposed 5-year renewal project are to: 1) identify the covariates of baseline substance abuse and sexual risks (including demographics, social risk measures, peer norms, abuse history, and mental health status) among a sample of 750 heterosexually active, not-in-treatment, club and prescription drug users ages 18 to 39 in Miami, Florida; 2) evaluate, through random assignment, the relative effectiveness of two intervention conditions and a waitlist control in reducing sex risks and drug use, as measured at 3-, 6- and 12-month follow-ups: Arm 1, an interviewer-administered comprehensive health and social risk assessment intervention (CAPI Intervention) similar to the baseline instrument used in the parent grant; Arm 2, an identical self-administered comprehensive assessment intervention (ACASI Intervention); and Arm 3, a waitlist control condition (Control). Outcome measures, including past 90-day counts of unprotected sex acts and days' drug use, will be obtained from brief risk behavior inventories at baseline and follow-ups; and 3) conduct qualitative process evaluation research with 40 participants in each study arm to contextualize the study findings and intervention outcomes. The proposed project is significant, as it responds to the need for brief interventions for a highly vulnerable, high risk population. The self-assessment intervention, if proven efficacious in reducing HIV risk, could be delivered at low cost and broad scale, and might well be adaptable to other high risk groups who are resistant to public health warnings and/or professional intervention.